Ink jet printing is accomplished by ejecting ink from a nozzle toward paper or another print medium. The ink may be driven toward the medium in a variety of ways. For example, in electrostatic printing, the ink is driven from a nozzle toward a medium by an electrostatic field. Another ink jet printing procedure, known as squeeze tube, employs a piezo-electric element in the ink nozzle. Electrically-caused distortions of the piezo-electric element pump the ink through the nozzle and toward the print medium. In still another ink jet printing procedure, known as thermal or bubble ink jet printing, the ink, is driven from the nozzle toward the print medium by the formation of an expanding vapor phase bubble in the nozzle. These various printing methods are described in "Output Hard Copy Devices," edited by Durbeck and Sherr, Academic Press, 1988 (see particularly Chapter 13, entitled, "Ink Jet Printing").
Ink compositions used in ink jet printers generally comprise deionized water, a water-soluble or water-miscible organic solvent, and a colorant. Generally, the colorant is a soluble dye or pigment. Unfortunately, inks comprising soluble dyes or pigments can exhibit many problems, such as poor water-fastness, poor light-fastness, clogging of the jetting channels as a result of solvent evaporation and changes in the solubility of the dye, dye crystallization, poor ink quality including ink bleeding and feathering, poor thermal stability, chemical instability, and case of oxidation.
The need for more light-fast inks for ink jet printing is increasing as photo images become more popular. Resistance to fading due to light has been aided in industrial products by incorporation of ultraviolet absorbers (UVAs). Commercially available UVAs are used in textile dying and for additives and coatings. TIo be effective, UVAs processed during textile dying typically require high temperature exposure for a duration of time; these high temperature requirements making the UVAs impractical for personal ink jet printing applications. UVAs used in the coating industry have limited solubility in water and therefore cannot be easily incorporated in conventional aqueous ink jet ink compositions.